HR: 0800h
AN: G21C-0683    [Abstracts]
TI: A Three-Dimensional Numerical Investigation of San Andreas Fault Configuration Through the San Gorgonio Pass
AU: * Dair, L
EM: LDair@geo.umass.edu
AF: University of Massachusetts, Department of Geosciences 611 North Pleasant St. 233 Morrill Science Center University of Massachusetts, Amherst, MA 01003-9297,
AU: Cooke, M
EM: cooke@geo.umass.edu
AF: University of Massachusetts, Department of Geosciences 611 North Pleasant St. 233 Morrill Science Center University of Massachusetts, Amherst, MA 01003-9297,
AB: The partitioning of deformation among strands of the San Andreas Fault through the San Gorgonio pass depends on fault geometry. We investigate three alternative three-dimensional configurations of the San Andreas Fault to explore the influence of fault geometry on uplift patterns and slip rates. One model has the commonly used vertical geometry for the system. Another uses the Southern California Earthquake Center Community Fault Model to include two north-dipping, discontinuous, alternative stands. We developed a third model that smoothly connects the north-dipping faults to adjacent segments. Regional transform loading is applied as slip at the distal edges of a deep detachment as well as along the distal portions of the primary fault segments. The model with vertical faults fails to produce uplift in the San Bernardino Mountains. Both of the north-dipping models produce significant uplift that may correspond to observations of recent uplift in the San Bernardino Mountains (Spotila et al, 1998). The vertical model has faster strike-slip rates while the north-dipping, discontinuous system has the slowest strike-slip rates. While the vertical model has the greatest net slip and more efficiently transmits deformation through the pass, the north-dipping fault configurations better match uplift patterns. We altered the continuous and north-dipping model to explore the effects of slip partitioning among the San Andreas and San Jacinto faults and secondary faults to the model. Debate continues about the slip partitioning between the Coachella Valley segment of the SAF and the San Jacinto fault. Our study suggests that slip portioning between the two faults has less of an effect on the slip rates and off fault deformation than fault geometry. The addition of secondary faults to the model significantly increases uplift in the northern San Bernardino Mountains. The senses of slip along secondary faults in the model are consistent with geologic observations. Continuing research investigates the evolution of the fault system of the San Gorgonio Pass. Geologic studies have assigned activation and deactivation times to each fault strand in the region. A sequence of numerical models investigates these transitions and the processes controlling fault system evolution.
DE: 1744 Tectonophysics
DE: 4255 Numerical modeling (0545, 0560)
DE: 8011 Kinematics of crustal and mantle deformation
DE: 8015 Local crustal structure
DE: 8111 Continental tectonics: strike-slip and transform
SC: Geodesy [G]
MN: 2007 Fall Meeting